At present, it is well known that energy accumulator systems and electric batteries can help to improve and optimize the management of electricity networks in various different ways. Mainly, two different divisions of battery systems, are detailed below:
1) Depending on the place where the electricity system is installed, it can be divided as follows:                1a) Consumption: batteries that are installed together with energy consumers. The batteries can modify the electrical energy consumption profiles displacing them to the hours with greatest available energy or cheaper energy. They can also help to give more uniform consumption profiles over time to simplify the work of the network managers. In this case, the batteries are operated by the energy consumer so that his electricity bill is as small as possible, bearing in mind the cost of the energy at different hours of the day and possible penalties can be imposed on him.        1b) Distribution: the batteries can be installed in electricity distribution substations and be another element in their management so that they can absorb fluctuations in production or consumption, or they can be used as an energy store in order to have it at peak demand hours. In this case, the batteries are operated by the system managers so that they aid towards the stable operation thereof (for example, helping to control frequency and voltage thereof) as well as reducing costs, avoiding expensive network support generation systems.        1c) Generation: energy generation plants can also have accumulator batteries to improve their integration in the electricity network, thus meeting network operator demands to improve the economic performance of the plants by being able to transfer off-peak hour generation to peak hours. In this case, the batteries are operated by the electricity plant managers to meet the network operator's legislation and maximize their profits from the sale of electricity.        
2) Depending on the battery operation mode, it can be divided as follows:                2a) Capacity for auxiliary network services: the batteries are controlled depending on the status of the electricity network to help its stability. Generally, these services require a power offer producible during a determined time that will be delivered in response to deviations in network parameters. Therefore, the payment tariffs of these services are usually by available power, sometimes complemented by the value of the energy delivered. A typical example is the control of the frequency in the network that will deviate from the rated frequency if the consumption and the production do not match at a certain time. Therefore, the batteries can offer a power band to deliver or consume from the electricity network so that it reacts, thus helping to equal production and consumption. Another example is voltage regulation in network nodes through the delivery or consumption of reactive power.        2b) Energy to optimize generation or consumption: for various reasons, energy prices differ at each hour of the day, and there may also be restrictions in the networks due to saturation. Therefore, batteries can be charged during certain times of the day and discharge during other times to optimize either the electricity bill or the generation revenue. This use entails a financial profit proportional to the energy delivered by the batteries. In the renewable plants, a typical use of batteries to optimize generation is the stabilization of the energy delivered by the plant avoiding power delivery fluctuations that are too fast, which may harm the stability of the electricity network whereto they are connected. Furthermore, the dynamics of this type of use are not always the same. A use to stabilize a consumption or a production variable throughout each hour of the day (“firming”) will have cycles in the range of minutes-hours. A use to move off-peak generation to peak generation may have one or two daily cycles. A use to avoid overloads in the network can have a few weekly or even monthly cycles.        
Furthermore, a battery system connected to an inverter may supply reactive power as a support to the network voltage independently from the charge status of the battery, only guaranteeing that it does not exceed the current limits in the equipment.
More specifically, a battery with storage capacity of 1 MWh can perform 2 daily cycles: one to load 1 MWh in night off-peak value and transfer it in morning peak hours, and another in the afternoon/evening off-peak hours and transfer it in peak night hours. However, a great potential for use of said battery the rest of the day is lost in performing just 1 or 2 cycles, and its management and operation can be clearly optimized.
The technical problem posed here is that energy accumulator systems and devices are currently designed to perform a single functionality (regulation of the power variations of a plant, regulation of network frequency, movement of energy from off-peak hours to peak hours, etc.), in many cases several batteries with different functions being combined at the same point, with the consequent financial cost entailed.
Typically, in a renewable plant, wherein an accumulator unit is necessary to optimize generation (avoid too fast fluctuations in the energy delivered to the network and/or move energy from certain hours of the day to others due to price or saturation), it will be gauged to the worst condition of the production year and is exclusively devoted to this service. However, as the production costs of the renewable plant are dependent on wind or solar resources and, therefore, are very variable, there are a great number of hours in the year where the accumulator system is underused.
A single accumulator unit will be typically formed by a set of individual systems that are connected in series and in parallel to build the system. Therefore, the set of accumulator units that have a single control unit that manages its joint operation is considered a single accumulator system. It is therefore a logical and not physical unit. A plant that contains several accumulator elements but that are managed from a single central control unit central operates in practice as a single accumulator system. The configuration of each of the system's accumulator elements for a specific service (which can be several different ones) is, therefore, considered as state of the art.